The present invention relates to a process for coloring granite which comprises permeating a colorant solution into granite followed by heating the granite to display gorgeous colors quite similar to those of native granite.
Granite colored in accordance with the process described above has gorgeous colors as well as excellent physical properties than native granite in terms of resistance to various factors such as water, weathering and impact, and has, in particular, no tendency to discoloration, resulting in fast color.
Granite, one of hard rocks, originally consisting of rock forming minerals such as feldspar, quartz, mica, pyroxene, amphibole, and so on is classified by its color into five of them such as white granite containing major proportions muscovite, black granite containing biotite as major mineral, red granite containing feldspar with approximately one percent of ferric oxide, brown granite containing brown substance created by rock weathering of the red granite, which, however, does not meet the demand due to its slight production, and greyish white granite which has been produced on massive commercial scale for decorative construction materials.
Coloration of granite according to the present invention can be applied to ordinary stone. However, according to one aspect of the present invention, there is provided a process for preparing colored granites by using greyish white and/or white granite.
Conventional process of coloring stone comprises dissolving an inorganic or organic pigment in solvent, subjecting the stone to physical treatments under pressure to soak or permeate the pigment solution into voids or gaps of the stone, and drying to develop pigment color in the stone itself.
This process has some disadvantages in the fact that the colorants or pigments are decomposed by heat or sunlight or easily leached out by water, resulting in discoloration which consequently may cause loss of its original color of the colorant or pigment.
Other conventional process has been carried out by treatment of stone or rock crystal at high temperatures to expand surface voids or gaps to provide easy permeation of colorant or pigment thereinto for improving coloration efficiency.
This kind of process, however, provides the products with potential discoloration and remarkable deterioration of physical properties such as weathering resistance, water resistance and impact resistance.
Another process discloses impregnation of pigment blended with thermosetting resin solution. This process creates poor impregnation only to provide surface coating as well as loss of natural beauty.